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Central and eastern associations of electroencephalographers, 53rd ski meeting
Electroencephalography and clinical Neurophysiology , 87 (1993) 4 7 P - 5 1 P
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~© 1993 Elsevier Scientific Publishers Ireland, Ltd. 0013-4694/93/$06.0(I
E E G 93073
Society proceedings
Central and Eastern Associations of Electroencephalographers, 53rd ski meeting La Sapini~re, Val David, Que., 18-20 February 1993
Secretary (EAEEG): Dr. Margaret C. McBride Uni~'ersity of Rochester School o f Medicine, P.O. Box 631, 601 Elmwood At,enue, Rochester, NY14642 (USA) ( R e c e i v e d for p u b l i c a t i o n : 26 A p r i l 1993) 1. Middle-latency auditory evoked potentials in epilepsy. - M.E. Drake, Jr., S.J. Weate and S.A. Newell (Ohio State University, Columbus, OH) Evoked and event-related potentials have been frequently studied in epilepsy. Middle-latency auditory evoked potentials (MLAEPs) have been recorded after cortical lesions and seizure surgery. We recorded M L A E P s in 14 patients with well-controlled complex partial and secondarily generalized seizures. M L A E P s were recorded with Cz-AI and Cz-A2, with 50 msec analysis time, 20-1000 Hz filter bandpass, and 20 k~V/div sensitivity. 4000 Hz alternating clicks were delivered at 5 . 4 / s e e through shielded headphones at 80 dB SL. Five h u n d r e d averages were recorded and replicated, and patients were compared to 10 age-matched neurologically and audiologically intact controls, N a and P;~ potentials did not differ in latency between patients and controls, although both were longer among seizure patients. P, was lower in amplitude in epileptics, but this difference was not significant. N,, was significantly increased in amplitude in complex partial seizure patients compared to controls, These findings accord with previous suggestions that M L A E P s may be generated subcortically but modulated by temporal lobe structures. M L A E P s my be of diagnostic value in differentiating temporal and extratemporal epilepsy. They may help clarify interictal cognitive or behavioral symptoms related to epilepsy or effects of antiepileptic medications. 2. Facilitation of motor evoked potentials by mental movement simulation of intrinsic hand muscles. - K. Knoebel, L.J. Streletz, M.H. Goodman and G. Herhison (Thomas Jefferson University, Philadelphia, PAl We studied the mechanisms underlying changes in amplitude, latency and motor mapping of motor evoked potentials (MEPs) observed after facilitation. MEPs obtained by transcranial magnetic stimulation (TMS) were studied in 6 healthy subjects at rest, after voluntary contraction of the abductor pollicis brevis (APB) muscle, and after a mental movement simulation (MMS) of intrinsic hand muscles (Roland et al. 1980). Focal stimulation of the motor cortex was accomplished with the aid of a flexible nylon grid using a magnetic coil and a magnetic stimulator. M E P s were measured and the motor representational area was mapped for the APB in each of the study conditions. The amplitude, latency and motor representational area were compared to resting responses. T h o u g h statistically significant increases in M E P amplitude were observed for both voluntary muscle contraction and the MMS states (Wilcoxon Signal
Rank Test P < 0.05), the M E P latency and scalp representational area were affected by voluntary contraction of the APB only. These data suggest that there are quantitative differences in the facilitative effects between voluntary contraction and mental effort alone. Further evidence of the role of the supplementary motor cortex (area 6) in cortical facilitation is inferred by these observations. 3. Subdural electrode array and brain tumor resection. - G.L. Moriarty, J.R. Gates, M.B. Dunn, R. Gregory, P.E. Penovich, M.D. Frost, F.J. Ritter and D. Kispert (The Minnesota Epilepsy Group of United and St. Paul Children's Hospitals, St. Paul, MN) Sixteen patients (ages 21-68; 9 females, 7 males) with intracranial neoplasms in close proximity to eloquent functional cortex underwent the placement of subdural electrode arrays (SEA) prior to total or partial tumor resection. All patients had MRI confirmation of tumor location. Selected patients had confirmation of speech and memory function by an intracarotid sodium amytal test. Thirteen patients with a history of seizures underwent video E E G monitoring with surface electrodes prior to SEA recording and functional cortical mapping. Comprehensive neuropsychological test batteries were performed and metastatic work-ups were also completed. Clinical follow-up has ranged from 3 to 16 months. O n e patient had the subdural electrode array removed within 18 h due to exacerbation of mass effect. All of the rest, however, tolerated SEA placement for 3-15 days without incident. In all cases, functional cortical mapping allowed a more aggressive surgical resection than would have been attempted without the information supplied. Areas of epileptogenesis identified from the subdural electrode array recording could also be included in the resection when they did not overlap with vital eloquent cortex. We submit that in properly selected cases, functional cortical mapping with subdural electrode arrays allows more aggressive brain tumor resection without increased complications. Details of this series will be discussed. 4. Description and prognostic value of spikes at electrocortieography for temporal Iobectomy. - O. Kanazawa, W.T. Blume and J.P. Girvin (University Hospital, London, Ont., Canada) Electrocorticography was performed in 87 patients for 30 min before and after temporal lobectomy under local anesthesia and its findings were correlated with classes of outcome: I = seizure-free; II = > 90% improved; Ill = 5 0 - 9 0 % improved; IV = not improved. Pre-resection spikes appeared more commonly in the hippocampus than in any other area with the temporal convexity being the next most c o m m o n location. Post-resection spikes were more corn-
48P mon at the temporal convexity than the orbital frontal and frontal parietal opercula areas. No consistent change in spike quantity between the first and last 10 min of post-resection recording occurred, Only in the hippocampus did spike abundance distinguish class I from other outcomes: 38 (50%) of 75 patients with at least 5 spikes/100 sec became seizure-free while only 1 (8%) of 12 patients with rarer spikes did so. Spikes were distinctly less abundant among patients with class IV outcomes in all areas except the frontal parietal opercula where they were sparse for all groups, Post-resection spikes were at least as abundant among favorable outcome classes (I, II) as in unfavorable classes (III, IV). Spike abundance did not distinguish class I from other groups. lnsula spikes were more abundant among patients with favorable outcomes (I, 11) than less favorable ones (III, IV). 5. The effect of spinal hemisections on amygdala-kindled convuisions. - L. Chert, P.A. Hwang a n d W. Melntyre Burnham (Bloorview Epilepsy Program, University of Toronto, Toronto, Ont., C a n a d a ) Traditionally it has been believed that seizure activity, arising in the brain, reaches the body via the direct descending pathways in the white matter of the spinal cord. This concept has been challenged, however, by the findings of Ninchoji et al. (1981), who demonstrated convulsions in the bodies of cortically kindled rats after bilateral hemisections of the spinal cord. In the present study, the effect of bilateral hemisections on amygdala-kindled convulsions has been investigated. Hemisections were made at C2 (right) and C5 (left) in Long-Evans rats following amygdala kindling to 10 stage 5 seizures. Sham surgery was done at corresponding levels in control animals, and convulsions were videotaped in both groups before and after surgery. A special feature of the present study is that completeness of hemisections was checked not only via light microscopy, but also with fluorescent dye tracers (True Blue). It was found that amygdala-kindled convulsions continued to be present in all subjects following bilateral spinal hemisections, although - in comparison to control animals - latency to onset was greater and more prominent tonus was seen. Both light microscopic examination and fluorescent tracers confirmed that all direct descending pathways have been completely destroyed. It appears that epileptic activity can spread from brain to spinal cord in the cornplete absence of direct descending pathways. 6. Frontal lobe epilepsy in the pediatric age group: clinical and electrographic features. - D. LaMoureux, S. Levy, E. Novotny and S. Spencer (Yale University School of Medicine, New Haven, CT)
Background, Frontal lobe seizure semiology is well described in adults. Electrographic findings are non-specific, demonstrating a continuum of interictal and ictal features. No systematic analysis of frontal lobe seizures has been done in children, Design/method. We reviewed the records of all patients under age 18 admitted to our Epilepsy Monitoring Unit from 1987 to 1992. In order to obtain a "'pure culture" of frontal lobe seizures, patients were selected who met the following criteria: (1) medically intractable complex partial seizures; (2) frontal lobe structural lesion; (3) "seizure-free" following frontal lesionectomy. Clinical and electrographic features in 4 such patients were reviewed in detail. Results. Age at the time of monitoring was 10-16 years, with seizure onset between 10 and 36 months. Clinical semiology was varied, ranging from brief "absence," to more complex motor manifestations, to more spectacular findings such as aggressive verbalization and complicated gesticulations. Scalp electrographic evidence for focal, regional or "generalized" epileptogenesis was documented. Pathology findings were cortical dysplasia (2), oligodendroglioma (1)
SOCIETY P R O C E E D I N G S and gliosis (1). Following resection, patients were seizure-free (5-24 months follow-up). Conclusion.Children representing a " p u r e culture" of frontal lobe seizures had clinical and electrographic features similar to those described in adults. Given the common trend of frontal lobe seizures to undergo rapid propagation, the slow process of myelination of major commissural systems, these findings are surprising 7. Generalized ictai eleetroencephalograpbic features after total cnrpus callosotomy. - L. DePaola, J.R. Gates, F.J. Ritter, M.B. Dunn, M.D. Frost and P.E. Penovich (The Minnesota Epilepsy Group of United and St. Paul Children's Hospitals, St. Paul, MN) Previous studies have clearly documented that corpus callosum section diminishes but does not completely abolish secondarily bilaterally synchronous interictal E E G discharges. Yet the effects of corpus callosum section on ictal E E G patterns has had limited review. Spencer et al. have previously suggested that although interictal discharges are demonstrated to be bilaterally synchronous after complete corpus callosum section, they cannot demonstrate preservation of bilaterally synchronous ictal discharges in 18 patients subjected to corpus callosotomy. We present 2 / 1 3 patients with complete callosotomy (of a recent series of 34 resected patients) as corroborated by MRI imaging who nonetheless still demonstrated ictal discharges that were bilaterally synchronous. Both bilaterally synchronous and independent ictal onsets were found postoperatively in these patients. This finding challenges the theory that the corpus callosum is the exclusive pathway involved in secondary ictal bilateral synchronous expression. Consistent with the interictal discharges it appears that pathways for secondary epileptogenesis continue to exist postoperatively even after complete corpus callosum division. 8. Sleep apnea and periodic leg movements (PLMs) in epilepsy. M.E. Drake, Jr., A. Pakalnis and S.A. Newell (Ohio State University, Columbus, OH) Sleepiness is a common complaint in the epilepsy clinic, and sleep disturbance is frequently reported by seizure patients. We carried out ambulatory nocturnal sleep recordings in 6 patients with complex partial seizures with and without secondary generalization, who had not yet started anticonvulsant treatment or whose medications had been discontinued. Five patients slept through the night, I of them only 3 h. Two patients had reduced sleep efficiency. Slow-wave sleep was reduced or absent in 4 patients, but no R E M sleep disturbance occurred. Two patients had no PLMs, 2 had no or few arousals and PLMs indices of 5 or less, and 2 had markedly elevated PLMs and arousal indices. No apneas or hypoapneas were recorded, but snoring indices were elevated in 2 patients. These findings suggest that sleep apnea is infrequent in unmedicated seizure patients. Some patients may have exaggerated PLMs with arousals, possibly related to epileptiform discharges but apparently not to seizures. Further study may clarify the relationship, if any, between epilepsy and PLMs. Supported in part by the Spaffort and Galbraith Research Funds, The Ohio State University College of Medicine. 9. The mask of wakefulness. - E.B. Cahoon (St. Joseph's Health Centre, Toronto, Ont., Canada) I have studied many patients for 45 years and have concluded that there is more than one kind of narcolepsy. I am presenting the findings of 212 patients with symptoms of narcolepsy studied from 1989 to 1991. 1 believe the " T e t r a d " of symptoms, excessive daytime somnolence, hypnagogic hallucinations, cataplexy, and sleep paralysis should
C E N T R A L A N D E A S T E R N A S S O C I A T I O N S O F EEGers SKI M E E T I N G be increased to include other symptoms. These consist of: attention deficit disorder, insomnia, alerting effect of codeine, nocturnal myoclonus, alerting effect of alcohol, difficulty speaking, sleep talking, phobias, panic attacks, sleep walking, difficulty swallowing, violence on wakening; the above are listed in descending order of occurrence which varies from 93% to 27%. Sleep rhythms were seen in the routine E E G - whether during hyperventilation or not, and all had other symptoms of narcolepsy. I conclude that this is a very significant finding, and not merely suggestive of the disease, I will show drug effects from a different series of 395 narcoleptic patients. None of my polysomnographic tested patients had " S O R E M P s . " 1 will discuss these findings showing numerous EEGs and charts showing the totals along with male and female distributions. 10. History of the evaluation of social problems of epileptic patients in Montreal. - G.M. R6millard, B.G. Zifldn and F. Andermann (Hfipital Neurologique, Montreal, Que., Canada)
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patients with intractable partial seizures. The exact m e c h a n i s m by which vagal nerve stimulation exerts its antiepileptic effect is not well understood. We have found the trigeminal complex to be a particularly good synaptic system for studying the action of antiepileptic drugs and have now investigated the effect of vagal nerve stimulation on this system. Electrical stimulation of the vagus nerve depressed the response of neurons in the spinal trigeminal nucleus to stimulation of the gasserian ganglion, increasing the latency of response and decreasing the number of spikes. The inhibitory effect of vagal nerve stimulation was enhanced by the iontophoretic administration of G A B A and blocked by iontophoresis of the G A B A A antagonist bicuculline. On the other hand, the iontophoresis of the G A B A n antagonist CGP 35348 had little or no effect. O u r experiments suggest that the antiepileptic action of vagal nerve stimulation is mediated by G A B A A mechanisms, in agreement with the observations of others suggesting that vagal nerve stimulation increases the release of GABA, as well as the extensive literature indicating that increased GABAergic function can decrease seizure susceptibility.
Although alienists, often superintendents, were aware of some of the social problems of epileptic patients, earlier programs and facilities were inadequately funded and had developed in the light of the traditional concepts about epilepsy. The first local study on the social problems of epileptic patients began in 1945. The medical staff and social workers who trained
13. EEG patterns in patients undergoing hemispherectomy evaluation. - L. C a r m a n t , J. Riviello, U. Kramer, S. Helmers, M. Mikati, J. Madsen, P.McL. Black and G.L. Holmes (Harvard Medical School, Boston, MA)
many epileptologists worked in close communication. 276 patients attending the weekly "seizure clinic" held by the Montreal Neurological Institute (NMI) staff in the outpatient department of the Royal Victoria Hospital were studied, The study had been encouraged by Wilder Penfield and William Lennox. Francis McNaughton and Antonio Barbeau provided guidance and Preston Robb helpful criticism of the resulting manuscript, The recommendations of this study are still applicable, In the 1970s the provincial government created local community social service centers (CLSC) and specific epilepsy groups have also developed, but coordination of social and medical interventions need
Hemispherectomy is a surgical option in patients with partial seizures and a hemiparesis. With its high rate of complications, it is often restricted to patients with unilateral epileptiform activity; presence of contralateral independent spikes is considered a poor prognostic marker. We report our experience with 12 patients who had hemispherectomies. Ten of 12 (83%) had bilateral, independent spikes. Nine of 12 (75%) remain seizure free 6 months to 29 years after surgery. Of the 10 patients with bilateral independent epileptic spikes on surface EEG, only 2 have persistent seizures. A pattern of suppression of background activity ipsilateral to the suspected abhormal hemisphere was seen in 8 and this correlated with a good
to be improved,
outcome in all despite 6 of 8 (75%) having bilateral independent spiking. Ten patients had long-term E E G and video monitoring (LTM). Two had a unilateral onset while 8 had bilateral onset
11. Subclinical status epileptieus in adults: prognosis and EEG features. - E.L. So a, P.A. Ahmann, K.H. Ruggles, K. Weatherford and S. Trudean (Marshfield Clinic, Marshfield, W1 and Mayo Clinic, Rochester, MN) Between July 1, 1986, and October 16, 1990, subclinical status epilepticus (SE) was detected in 22 adults at the Marshfield Medical Center. Unlike the report by Treiman et al. (Epilepsy Res., 1990, 3: 49-60), the majority of patients (19 of 22) had only discrete electrographic seizures. In 2 patients, E E G abnormality fluctuated within the same recording between the discrete seizure pattern and the periodic epileptiform discharge pattern. Only 1 patient had periodic epileptiform discharge pattern. None developed a progressive sequence of E E G patterns (i.e., discrete seizures, merging seizures with waxing and waning of ictal discharges, continuous ictal discharges, continuous ictal discharges with flat periods, and periodic epileptiform discharges on a flat background). W h e n compared to 23 patients with clinical SE during the same period of time, there was no difference in age distribution. Subclinical SE was more difficult to control than clinical SE. Subclinical SE was also more likely to be associated with acute cerebral lesions, and mortality was higher at 60 days after onset. 12. Effect of vagal nerve stimulation on a synaptic system model. G.H. Fromm and K. Sun (University of Pittsburgh, Pittsburgh, PA) Intermittent stimulation of the vagus nerve has been found to prevent or reduce seizures in both experimental animals and in
although in 2 the discharges were higher in amplitude ipsilateral to the abnormal hemisphere. Three had invasive L T M which showed lateralized onset. We conclude that bilateral independent spikes are frequent and not systematically associated with a poor outcome. In patients with bilateral spiking, the presence of ipsilateral background suppression supports a good outcome. Finally, if contralateral seizure onset is suspected, invasive monitoring can clarify seizure onset. 14. SPECT scan findings in the evaluation of hemispherectomy for intractable seizures: a predictor of favorable outcome. - L. C a r m a n t , J. Riviello, U. Kramer, S. Helmers, M. Mikati, J. Madsen, P.MeL. Black and G.L. Holmes (Harvard Medical School, Boston, MA) Hemispherectomy for seizure control is associated with improvemeat in 80-90% with 7 0 - 8 0 % being seizure free. However, some centers still r e c o m m e n d callosotomy over hemispherectomy because of the latter's high rate of complications, mainly superficial hemosiderosis. Also, patients with bilateral anomalies on E E G or M R I often are not considered because of the additional risk of recurrence. Here, we describe our experience since 1990, using interictal SPECT scan to assess children between 15 months and 9 years of age in their evaluation for hemispherectomy. Five patients had bilateral findings on surface EEG, one of whom also had bilateral abnormalities on MRI. To pursue hemispherectomy in these patients, we obtained an interictal SPECT scan and surface monitoring in all and depth monitoring in 3. All SPECT scans
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SOCIETY P R O C E E D I N G S
lateralized to the same hemisphere as the ictal discharges on invasive monitoring and did not show contralateral changes in the others, Hemispherectomy was performed on all 5 children and all are seizure free 6-20 months after surgery. This study demonstrates that SPECT scan is a significant adjunct in investigation for hemispherectomy. Lateralized findings on SPECT strongly support a favorable outcome regardless of surface E E G findings,
15. Scalp EEG abnormalities in relation to unilateral mesial temporal atrophy. - A. Gambardella, F. Cendes, J. Gotman and F. A n d e r m a n n (Montreal Neurological Institute, Montreal, Que., Canada)
Objectit,es. To assess the relationship between electroencephalographic abnormalities and mesial temporal atrophy in temporal lobe epilepsy (TLE). Background. MR1 volumetric studies show hippocampus and amygdala atrophy in many T L E patients. The role of this atrophy in the pathogenesis of T L E remains unclear and we attempted to relate it to E E G findings, Methods. We reviewed preoperative E E G s with scalp and sphenoidal electrodes in 27 T L E patients in whom MRI volumetric m e a s u r e m e n t s had shown unilateral amygdala a n d / o r hippocampus atrophy compared to matched controls. Results. Theta activity was observed in 2 3 / 2 7 patients but correluted poorly with atrophy (bilateral in 18/23). Delta activity was present in 2 3 / 2 7 patients and correlated well with atrophy (unilateral or clear ipsilateral predominance in 22/23). Spikes were found in 2 6 / 2 7 patients; they were ipsilateral to atrophy in 18 patients and bilateral in 8. 73 ictal onsets were analyzed: 34 (46%) were ipsilateral, 2 (3%) contralateral, 19 (26%) bilateral, and 18 (25%) undeterminate. Conclusion. T h e results show clearly that spikes and seizure onsets can be widespread or bilateral even in patients where unilateral mesial temporal atrophy is the only MRI abnormality. However, delta activity almost always coincides with the side of atrophy, Further investigations are required to establish the clinical significance of contralateral epileptiform activity.
16. Analysis of amygdaloid volume in patients with chronic temporal lobe seizures. - W.B. Bare a,b, p.j. Snyder b, M. Ashtari ¢ and N. Schaul a (Departments of a Neurology, b Psychiatry and c Radiology, Long Island Jewish Medical Center, New Hyde Park, NY) Results from recent research using M R imaging and computerized volumetric techniques have indicated that unilateral temporal lobe E E G foci are often accompanied by significant lateralized reductions in hippocampal volume. Very few studies have used computerized morphometry to examine the amygdala in patients with unilateral temporal lobe seizures. In this study, measures of left and right amygdaloid volumes were computed from flash M R images from 31 presurgical patients (16 left temporal, 15 right temporal) and 27 age- and sex-matched controls. A multivariate analysis of variance revealed a significant group by hemisphere interaction ( P < 0,001). Post hoc analyses indicated a lack of asymmetry in patients with right temporal lobe foci. Lateralized reductions in amygdaloid volume correctly predicted the laterality of the E E G seizure focus in 65% of the patient sample. Additional analyses revealed a high correlation between left and right amygdaloid volumes and a lack of correlation between amygdaloid and hippocampal volumes. O u r findings indicute that reductions of amygdaloid volume are associated with unilateral temporal lobe seizures, though the value of using these volumes to classify the laterality of the E E G seizure focus in surgical candidates remains unclear at this time.
17. Changes of the posterior tibial nerve somatosensory evoked potential in sleep. - M. Yeh, T. Yamada, Y. Noguehi, M. Matsubara, G. Shiraishi, S.-i. Kagimoto and N. U r u s h i b a r a (University of Iowa, College of Medicine, Iowa City, IA) We studied the changes of the posterior tibial nerve sensory evoked potential (PTN-SEP) topographically at various stages of sleep. Seven normal subjects had PTN-SEPs recorded from 16 closely spaced scalp electrodes (1.5-2 cm) centered at Cz, Standard peak nomenclature was used in assessing all SEPs which included P31, N35, N37, P40, N50, P31, P37 and P45. P31 and P35 were diffusely distributed but N37 was located at the contralateral hemisphere. P40 and N50 were paradoxically lateralized to the ipsilateral side. In all subjects, N37, P40 and N50 peaks showed a progressive latency prolongation (1.29 + 0.94 msec for N37, 1.68 ± 0.81 msec for P40, and 2.41 ± 1.04 msec for P50) with a concomitant increase in the N35-P40 peak-to-peak amplitude (1.08 ± 0.52 ~V) as stages 3 and 4 sleep were approached. R E M sleep showed a significant latency prolongation for N37 while P40 remained unchanged. Stages 1 and 2 of sleep showed no significant change in latencies or amplitudes when cornpared to the awake state. Previous studies on the median nerve have shown a similar pattern of latency prolongation. The latencies of the median N20 and P26 potentials behave in a similar m a n n e r to the tibial N37 and P40 respectively as noted above. These similarities in sleep may indicate these peaks to be analogous potentials between the two nerves. 18. Unique characteristics in the SEP recovery function for the pudendal nerve, - G. Shiraishi, T. Yamada, Y. Noguchi, M. Matsubara, S.-i. Kajimoto and N. Urshibara (University of Iowa College of Medicine, Iowa City, IA) Using a paired stimulus paradigm, we studied the recovery functions of somatosensory evoked potentials (SEPs) for the dorsal nerve of the penis (DNP-SEP) and found significant differences from other peripheral nerve SEPs. The paired stimuli, S1 and $2, were tested using interstimulus intervals (ISis) of l, 2, 5, 10, 30, 50 and 70 msec. The derived test ($2) response influenced by the preceding conditioning (1) stimulus was obtained by subtracting the response to a single stimulus (S1 only) from the response to a paired ( $ 1 + $ 2 ) stimulus. The recovery curves for the DNP-SEP were quite different from other SEPs. First, there was no significant suppression for stimuli of short ISis, except for 1 msec ISis where the DNP-SEP was noted to be almost absent. Second, the amplitude facilitation after 2 msec IS1 was far larger than that observed in other peripheral nerve SEPs. Finally, in contrast to the maximum suppression of other peripheral nerve SEPs at 30-50 msec ISI, the DNP-SEP showed maximum facilitation at 30 msec ISI. We propose that certain anatomical a n d / o r physiological characteristics are responsible for the remarkable amplitude facilitation of DNP-SEP. 19. Of mice a n d men: a case for brain-stem origin of short lasting nocturnal paroxysmal dystonia. - J.L. Burchfiel, G. Erha, C.D. Applegate, M.J. Berg a n d L. Oestreich (Comprehensive Epilepsy Program, University of Rochester, Rochester, NY) The pathogenesis and classification of "nocturnal paroxysmal dystonia" (NPD) remains obscure. It has been suggested that this syndrome represents a form of epilepsy, perhaps involving frontal or extrapyramidal structures. We present a case (patient MP) with a triad of symptoms: (1) a sleep disturbance characterized by frequent arousals from slow-wave sleep and, possibly, decreased R E M sleep; (2) arousals from slow-wave sleep accompanied by dyskinetic and dystonic movements (NPD); and (3) occasional tonic seizures occurring in association with the N P D episodes. The semiology of MP's tonic seizures is different from that typically seen in h u m a n general-
C E N T R A L A N D E A S T E R N A S S O C I A T I O N S OF E E G e r s SKI M E E T I N G ized seizure disorders and is essentially identical to that of mice receiving maximal electroshock (MES). MES tonic seizures in laboratory animals have been clearly demonstrated to depend on brain-stem structures. By analogy we suggest that MP's tonic seizures have a brain-stem origin. Most likely, MP's frequent arousals also involve brain-stem pathophysiology. Therefore, we advance the unifying hypothesis that all of MP's symptoms, including NPD, have a brain-stem origin involving structures which control s l e e p / w a k e f u l n e s s cycles and regulate associated muscle tone and movement. This case suggests that nocturnal paroxysmal dystonia is primarily a brain-stem sleep disorder,
20. Ietal SEEG propagation in surgically resistant temporal lobe epilepsy. - C. Adam, F. Richer and J.-M. Saint-Hilaire (Hfipital Notre-Dame, Montreal, Que., Canada) In temporal lobe epilepsy (TLE), studies using intracerebral seizure recordings (SEEG) have suggested that a short seizure propagation time to the contralateral temporal lobe is related to poor surgical outcome. However, our observations using a modified Talairach implantation method with electrodes in temporal and frontal lobes suggested that the first site of extratemporal propagation is most often the ipsilateral frontal lobe. We thus examined ictal SEEG characteristics in 3 matched groups of 7 T L E patients (resistants, cured, intermediate), taking into account the propagation to the frontal lobes. Resistant patients did not have any lesion outside the temporal lobe on CT scan or ictal S E E G characteristics of multifocality. Poor surgical outcome was related to: (1) the presence of widespread ictal onsets, (2) more frequent short ( < 1 sec) extratemporal propagation times, and (3) shorter m i n i m u m extratemporal propagation times (resistant group: 3.6 sec; cured group: 7.1 sec; intermediate group: 12.6 see). The data suggest that extent of SEEG ictal onset and speed of extratemporal (primarily frontal) propagation can be useful predictors of resistance to surgery for unilateral TLE. 21. Relationship between spike-waves and periodic leg movements in an adult with absence seizures. - B. Ehrenberg (Tufts University School of Medicine, Boston, MA) l have previously noted that adults with absence epilepsy have periodic leg movements (PLMs) of sleep. O n e such patient is a 30-year-old w o m a n whose nocturnal polysomnogram was examined in detail. The patient had a total sleep time (TST) of 7.4 h divided into 4 cycles 100-120 min in length with R E M at the end of each cycle but the second. There was an increased a m o u n t of stage 1 (21% of TST) at the expense of stage 2 (40%) and R E M (12%) while stages 3 - 4 were present in normal proportion (27%). There were 5
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brief awakenings. There were no apneas or hypopneas. There were 94 PLMs ( 1 2 . 7 / h of sleep); of these 60 (64%) were associated with arousals for a total arousal index of 8.7/h. There were 783 spike-wave bursts, usually seen as single or double complexes, at 2 3 Hz. The spike-wave complexes (SWCs) were densest in the first half of the night while the PLMs were clustered in the 3rd quarter of the night. Nevertheless, during the 3rd quarter, SWCs coincided with PLMs 59 times (63% of all PLMs), suggesting a shared trigger mechanism. Nine (15%) of the P L M / S W C pairings were also associated with an immediately following arousal pattern, not usually a feature of SWCs during sleep.
22. Electrocorticography for children with complex partial seizures undergoing excisional surgery. - P.A. Hwang, S.Y. Kwan, H. Otsubo and H.J. Hoffman (Bloorview Epilepsy Research Program and University of Toronto, Toronto, Ont., Canada) The role of intraoperative ECoG for excisional surgery in patients with intractable complex partial seizures has been recognised for over 50 years. Recently, however, a controversy arose over the value of post-excisional E C o G in adults undergoing anterior temporal lobectomy. We examined the question whether ECoG contributes to the surgical treatment of children with intractable complex partial seizures of temporal and extratemporal origin. In a retrospective study of 50 cases at the Hospital for Sick Children in Toronto undergoing excisional surgery between 1974 and 1991, all underwent E C o G at craniotomy, using a 4 x 4 or 4 × 5 electrode array under neuroleptic anesthesia (fentanyl and droperidol) from age 6 to 18 years, and general anesthesia under age 5 years with the nitrous oxide discontinued during the ECoG. For temporal lobectomy where the presurgical evaluation suggested mesial temporal dysfunction, depth electrode recording from the hippocampus at ECoG was also performed. There were 34 temporal and 16 extratemporal cases, with a follow up of 2 years or greater, and the seizure outcome was graded as I (seizure free, no drugs), II (seizure free, on drugs), III ( > 50% reduction), and IV ( < 50% reduction in seizures). Worthwhile iraprovement (grades I, II and II1 combined) was found in 3 0 / 3 4 cases (88%) after temporal lobectomy, and in 15/16 cases (93v/~) after extratemporal excision, but 1 died post-operatively. The post-excisional ECoG grade ( A - E ) did not correlate well with seizure outcome, although 2 cases with grade C (moderate residual epileptiform activity) had poor seizure outcome (grade IV) after temporal lobectomy, and 1 case after extratemporal excision. Although E C G is invaluable for localization of epileptogenic areas in both temporal and extratemporal excisions in children, its prognostic significance requires further study.
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~© 1993 Elsevier Scientific Publishers Ireland, Ltd. 0013-4694/93/$06.0(I
E E G 93073
Society proceedings
Central and Eastern Associations of Electroencephalographers, 53rd ski meeting La Sapini~re, Val David, Que., 18-20 February 1993
Secretary (EAEEG): Dr. Margaret C. McBride Uni~'ersity of Rochester School o f Medicine, P.O. Box 631, 601 Elmwood At,enue, Rochester, NY14642 (USA) ( R e c e i v e d for p u b l i c a t i o n : 26 A p r i l 1993) 1. Middle-latency auditory evoked potentials in epilepsy. - M.E. Drake, Jr., S.J. Weate and S.A. Newell (Ohio State University, Columbus, OH) Evoked and event-related potentials have been frequently studied in epilepsy. Middle-latency auditory evoked potentials (MLAEPs) have been recorded after cortical lesions and seizure surgery. We recorded M L A E P s in 14 patients with well-controlled complex partial and secondarily generalized seizures. M L A E P s were recorded with Cz-AI and Cz-A2, with 50 msec analysis time, 20-1000 Hz filter bandpass, and 20 k~V/div sensitivity. 4000 Hz alternating clicks were delivered at 5 . 4 / s e e through shielded headphones at 80 dB SL. Five h u n d r e d averages were recorded and replicated, and patients were compared to 10 age-matched neurologically and audiologically intact controls, N a and P;~ potentials did not differ in latency between patients and controls, although both were longer among seizure patients. P, was lower in amplitude in epileptics, but this difference was not significant. N,, was significantly increased in amplitude in complex partial seizure patients compared to controls, These findings accord with previous suggestions that M L A E P s may be generated subcortically but modulated by temporal lobe structures. M L A E P s my be of diagnostic value in differentiating temporal and extratemporal epilepsy. They may help clarify interictal cognitive or behavioral symptoms related to epilepsy or effects of antiepileptic medications. 2. Facilitation of motor evoked potentials by mental movement simulation of intrinsic hand muscles. - K. Knoebel, L.J. Streletz, M.H. Goodman and G. Herhison (Thomas Jefferson University, Philadelphia, PAl We studied the mechanisms underlying changes in amplitude, latency and motor mapping of motor evoked potentials (MEPs) observed after facilitation. MEPs obtained by transcranial magnetic stimulation (TMS) were studied in 6 healthy subjects at rest, after voluntary contraction of the abductor pollicis brevis (APB) muscle, and after a mental movement simulation (MMS) of intrinsic hand muscles (Roland et al. 1980). Focal stimulation of the motor cortex was accomplished with the aid of a flexible nylon grid using a magnetic coil and a magnetic stimulator. M E P s were measured and the motor representational area was mapped for the APB in each of the study conditions. The amplitude, latency and motor representational area were compared to resting responses. T h o u g h statistically significant increases in M E P amplitude were observed for both voluntary muscle contraction and the MMS states (Wilcoxon Signal
Rank Test P < 0.05), the M E P latency and scalp representational area were affected by voluntary contraction of the APB only. These data suggest that there are quantitative differences in the facilitative effects between voluntary contraction and mental effort alone. Further evidence of the role of the supplementary motor cortex (area 6) in cortical facilitation is inferred by these observations. 3. Subdural electrode array and brain tumor resection. - G.L. Moriarty, J.R. Gates, M.B. Dunn, R. Gregory, P.E. Penovich, M.D. Frost, F.J. Ritter and D. Kispert (The Minnesota Epilepsy Group of United and St. Paul Children's Hospitals, St. Paul, MN) Sixteen patients (ages 21-68; 9 females, 7 males) with intracranial neoplasms in close proximity to eloquent functional cortex underwent the placement of subdural electrode arrays (SEA) prior to total or partial tumor resection. All patients had MRI confirmation of tumor location. Selected patients had confirmation of speech and memory function by an intracarotid sodium amytal test. Thirteen patients with a history of seizures underwent video E E G monitoring with surface electrodes prior to SEA recording and functional cortical mapping. Comprehensive neuropsychological test batteries were performed and metastatic work-ups were also completed. Clinical follow-up has ranged from 3 to 16 months. O n e patient had the subdural electrode array removed within 18 h due to exacerbation of mass effect. All of the rest, however, tolerated SEA placement for 3-15 days without incident. In all cases, functional cortical mapping allowed a more aggressive surgical resection than would have been attempted without the information supplied. Areas of epileptogenesis identified from the subdural electrode array recording could also be included in the resection when they did not overlap with vital eloquent cortex. We submit that in properly selected cases, functional cortical mapping with subdural electrode arrays allows more aggressive brain tumor resection without increased complications. Details of this series will be discussed. 4. Description and prognostic value of spikes at electrocortieography for temporal Iobectomy. - O. Kanazawa, W.T. Blume and J.P. Girvin (University Hospital, London, Ont., Canada) Electrocorticography was performed in 87 patients for 30 min before and after temporal lobectomy under local anesthesia and its findings were correlated with classes of outcome: I = seizure-free; II = > 90% improved; Ill = 5 0 - 9 0 % improved; IV = not improved. Pre-resection spikes appeared more commonly in the hippocampus than in any other area with the temporal convexity being the next most c o m m o n location. Post-resection spikes were more corn-
48P mon at the temporal convexity than the orbital frontal and frontal parietal opercula areas. No consistent change in spike quantity between the first and last 10 min of post-resection recording occurred, Only in the hippocampus did spike abundance distinguish class I from other outcomes: 38 (50%) of 75 patients with at least 5 spikes/100 sec became seizure-free while only 1 (8%) of 12 patients with rarer spikes did so. Spikes were distinctly less abundant among patients with class IV outcomes in all areas except the frontal parietal opercula where they were sparse for all groups, Post-resection spikes were at least as abundant among favorable outcome classes (I, II) as in unfavorable classes (III, IV). Spike abundance did not distinguish class I from other groups. lnsula spikes were more abundant among patients with favorable outcomes (I, 11) than less favorable ones (III, IV). 5. The effect of spinal hemisections on amygdala-kindled convuisions. - L. Chert, P.A. Hwang a n d W. Melntyre Burnham (Bloorview Epilepsy Program, University of Toronto, Toronto, Ont., C a n a d a ) Traditionally it has been believed that seizure activity, arising in the brain, reaches the body via the direct descending pathways in the white matter of the spinal cord. This concept has been challenged, however, by the findings of Ninchoji et al. (1981), who demonstrated convulsions in the bodies of cortically kindled rats after bilateral hemisections of the spinal cord. In the present study, the effect of bilateral hemisections on amygdala-kindled convulsions has been investigated. Hemisections were made at C2 (right) and C5 (left) in Long-Evans rats following amygdala kindling to 10 stage 5 seizures. Sham surgery was done at corresponding levels in control animals, and convulsions were videotaped in both groups before and after surgery. A special feature of the present study is that completeness of hemisections was checked not only via light microscopy, but also with fluorescent dye tracers (True Blue). It was found that amygdala-kindled convulsions continued to be present in all subjects following bilateral spinal hemisections, although - in comparison to control animals - latency to onset was greater and more prominent tonus was seen. Both light microscopic examination and fluorescent tracers confirmed that all direct descending pathways have been completely destroyed. It appears that epileptic activity can spread from brain to spinal cord in the cornplete absence of direct descending pathways. 6. Frontal lobe epilepsy in the pediatric age group: clinical and electrographic features. - D. LaMoureux, S. Levy, E. Novotny and S. Spencer (Yale University School of Medicine, New Haven, CT)
Background, Frontal lobe seizure semiology is well described in adults. Electrographic findings are non-specific, demonstrating a continuum of interictal and ictal features. No systematic analysis of frontal lobe seizures has been done in children, Design/method. We reviewed the records of all patients under age 18 admitted to our Epilepsy Monitoring Unit from 1987 to 1992. In order to obtain a "'pure culture" of frontal lobe seizures, patients were selected who met the following criteria: (1) medically intractable complex partial seizures; (2) frontal lobe structural lesion; (3) "seizure-free" following frontal lesionectomy. Clinical and electrographic features in 4 such patients were reviewed in detail. Results. Age at the time of monitoring was 10-16 years, with seizure onset between 10 and 36 months. Clinical semiology was varied, ranging from brief "absence," to more complex motor manifestations, to more spectacular findings such as aggressive verbalization and complicated gesticulations. Scalp electrographic evidence for focal, regional or "generalized" epileptogenesis was documented. Pathology findings were cortical dysplasia (2), oligodendroglioma (1)
SOCIETY P R O C E E D I N G S and gliosis (1). Following resection, patients were seizure-free (5-24 months follow-up). Conclusion.Children representing a " p u r e culture" of frontal lobe seizures had clinical and electrographic features similar to those described in adults. Given the common trend of frontal lobe seizures to undergo rapid propagation, the slow process of myelination of major commissural systems, these findings are surprising 7. Generalized ictai eleetroencephalograpbic features after total cnrpus callosotomy. - L. DePaola, J.R. Gates, F.J. Ritter, M.B. Dunn, M.D. Frost and P.E. Penovich (The Minnesota Epilepsy Group of United and St. Paul Children's Hospitals, St. Paul, MN) Previous studies have clearly documented that corpus callosum section diminishes but does not completely abolish secondarily bilaterally synchronous interictal E E G discharges. Yet the effects of corpus callosum section on ictal E E G patterns has had limited review. Spencer et al. have previously suggested that although interictal discharges are demonstrated to be bilaterally synchronous after complete corpus callosum section, they cannot demonstrate preservation of bilaterally synchronous ictal discharges in 18 patients subjected to corpus callosotomy. We present 2 / 1 3 patients with complete callosotomy (of a recent series of 34 resected patients) as corroborated by MRI imaging who nonetheless still demonstrated ictal discharges that were bilaterally synchronous. Both bilaterally synchronous and independent ictal onsets were found postoperatively in these patients. This finding challenges the theory that the corpus callosum is the exclusive pathway involved in secondary ictal bilateral synchronous expression. Consistent with the interictal discharges it appears that pathways for secondary epileptogenesis continue to exist postoperatively even after complete corpus callosum division. 8. Sleep apnea and periodic leg movements (PLMs) in epilepsy. M.E. Drake, Jr., A. Pakalnis and S.A. Newell (Ohio State University, Columbus, OH) Sleepiness is a common complaint in the epilepsy clinic, and sleep disturbance is frequently reported by seizure patients. We carried out ambulatory nocturnal sleep recordings in 6 patients with complex partial seizures with and without secondary generalization, who had not yet started anticonvulsant treatment or whose medications had been discontinued. Five patients slept through the night, I of them only 3 h. Two patients had reduced sleep efficiency. Slow-wave sleep was reduced or absent in 4 patients, but no R E M sleep disturbance occurred. Two patients had no PLMs, 2 had no or few arousals and PLMs indices of 5 or less, and 2 had markedly elevated PLMs and arousal indices. No apneas or hypoapneas were recorded, but snoring indices were elevated in 2 patients. These findings suggest that sleep apnea is infrequent in unmedicated seizure patients. Some patients may have exaggerated PLMs with arousals, possibly related to epileptiform discharges but apparently not to seizures. Further study may clarify the relationship, if any, between epilepsy and PLMs. Supported in part by the Spaffort and Galbraith Research Funds, The Ohio State University College of Medicine. 9. The mask of wakefulness. - E.B. Cahoon (St. Joseph's Health Centre, Toronto, Ont., Canada) I have studied many patients for 45 years and have concluded that there is more than one kind of narcolepsy. I am presenting the findings of 212 patients with symptoms of narcolepsy studied from 1989 to 1991. 1 believe the " T e t r a d " of symptoms, excessive daytime somnolence, hypnagogic hallucinations, cataplexy, and sleep paralysis should
C E N T R A L A N D E A S T E R N A S S O C I A T I O N S O F EEGers SKI M E E T I N G be increased to include other symptoms. These consist of: attention deficit disorder, insomnia, alerting effect of codeine, nocturnal myoclonus, alerting effect of alcohol, difficulty speaking, sleep talking, phobias, panic attacks, sleep walking, difficulty swallowing, violence on wakening; the above are listed in descending order of occurrence which varies from 93% to 27%. Sleep rhythms were seen in the routine E E G - whether during hyperventilation or not, and all had other symptoms of narcolepsy. I conclude that this is a very significant finding, and not merely suggestive of the disease, I will show drug effects from a different series of 395 narcoleptic patients. None of my polysomnographic tested patients had " S O R E M P s . " 1 will discuss these findings showing numerous EEGs and charts showing the totals along with male and female distributions. 10. History of the evaluation of social problems of epileptic patients in Montreal. - G.M. R6millard, B.G. Zifldn and F. Andermann (Hfipital Neurologique, Montreal, Que., Canada)
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patients with intractable partial seizures. The exact m e c h a n i s m by which vagal nerve stimulation exerts its antiepileptic effect is not well understood. We have found the trigeminal complex to be a particularly good synaptic system for studying the action of antiepileptic drugs and have now investigated the effect of vagal nerve stimulation on this system. Electrical stimulation of the vagus nerve depressed the response of neurons in the spinal trigeminal nucleus to stimulation of the gasserian ganglion, increasing the latency of response and decreasing the number of spikes. The inhibitory effect of vagal nerve stimulation was enhanced by the iontophoretic administration of G A B A and blocked by iontophoresis of the G A B A A antagonist bicuculline. On the other hand, the iontophoresis of the G A B A n antagonist CGP 35348 had little or no effect. O u r experiments suggest that the antiepileptic action of vagal nerve stimulation is mediated by G A B A A mechanisms, in agreement with the observations of others suggesting that vagal nerve stimulation increases the release of GABA, as well as the extensive literature indicating that increased GABAergic function can decrease seizure susceptibility.
Although alienists, often superintendents, were aware of some of the social problems of epileptic patients, earlier programs and facilities were inadequately funded and had developed in the light of the traditional concepts about epilepsy. The first local study on the social problems of epileptic patients began in 1945. The medical staff and social workers who trained
13. EEG patterns in patients undergoing hemispherectomy evaluation. - L. C a r m a n t , J. Riviello, U. Kramer, S. Helmers, M. Mikati, J. Madsen, P.McL. Black and G.L. Holmes (Harvard Medical School, Boston, MA)
many epileptologists worked in close communication. 276 patients attending the weekly "seizure clinic" held by the Montreal Neurological Institute (NMI) staff in the outpatient department of the Royal Victoria Hospital were studied, The study had been encouraged by Wilder Penfield and William Lennox. Francis McNaughton and Antonio Barbeau provided guidance and Preston Robb helpful criticism of the resulting manuscript, The recommendations of this study are still applicable, In the 1970s the provincial government created local community social service centers (CLSC) and specific epilepsy groups have also developed, but coordination of social and medical interventions need
Hemispherectomy is a surgical option in patients with partial seizures and a hemiparesis. With its high rate of complications, it is often restricted to patients with unilateral epileptiform activity; presence of contralateral independent spikes is considered a poor prognostic marker. We report our experience with 12 patients who had hemispherectomies. Ten of 12 (83%) had bilateral, independent spikes. Nine of 12 (75%) remain seizure free 6 months to 29 years after surgery. Of the 10 patients with bilateral independent epileptic spikes on surface EEG, only 2 have persistent seizures. A pattern of suppression of background activity ipsilateral to the suspected abhormal hemisphere was seen in 8 and this correlated with a good
to be improved,
outcome in all despite 6 of 8 (75%) having bilateral independent spiking. Ten patients had long-term E E G and video monitoring (LTM). Two had a unilateral onset while 8 had bilateral onset
11. Subclinical status epileptieus in adults: prognosis and EEG features. - E.L. So a, P.A. Ahmann, K.H. Ruggles, K. Weatherford and S. Trudean (Marshfield Clinic, Marshfield, W1 and Mayo Clinic, Rochester, MN) Between July 1, 1986, and October 16, 1990, subclinical status epilepticus (SE) was detected in 22 adults at the Marshfield Medical Center. Unlike the report by Treiman et al. (Epilepsy Res., 1990, 3: 49-60), the majority of patients (19 of 22) had only discrete electrographic seizures. In 2 patients, E E G abnormality fluctuated within the same recording between the discrete seizure pattern and the periodic epileptiform discharge pattern. Only 1 patient had periodic epileptiform discharge pattern. None developed a progressive sequence of E E G patterns (i.e., discrete seizures, merging seizures with waxing and waning of ictal discharges, continuous ictal discharges, continuous ictal discharges with flat periods, and periodic epileptiform discharges on a flat background). W h e n compared to 23 patients with clinical SE during the same period of time, there was no difference in age distribution. Subclinical SE was more difficult to control than clinical SE. Subclinical SE was also more likely to be associated with acute cerebral lesions, and mortality was higher at 60 days after onset. 12. Effect of vagal nerve stimulation on a synaptic system model. G.H. Fromm and K. Sun (University of Pittsburgh, Pittsburgh, PA) Intermittent stimulation of the vagus nerve has been found to prevent or reduce seizures in both experimental animals and in
although in 2 the discharges were higher in amplitude ipsilateral to the abnormal hemisphere. Three had invasive L T M which showed lateralized onset. We conclude that bilateral independent spikes are frequent and not systematically associated with a poor outcome. In patients with bilateral spiking, the presence of ipsilateral background suppression supports a good outcome. Finally, if contralateral seizure onset is suspected, invasive monitoring can clarify seizure onset. 14. SPECT scan findings in the evaluation of hemispherectomy for intractable seizures: a predictor of favorable outcome. - L. C a r m a n t , J. Riviello, U. Kramer, S. Helmers, M. Mikati, J. Madsen, P.MeL. Black and G.L. Holmes (Harvard Medical School, Boston, MA) Hemispherectomy for seizure control is associated with improvemeat in 80-90% with 7 0 - 8 0 % being seizure free. However, some centers still r e c o m m e n d callosotomy over hemispherectomy because of the latter's high rate of complications, mainly superficial hemosiderosis. Also, patients with bilateral anomalies on E E G or M R I often are not considered because of the additional risk of recurrence. Here, we describe our experience since 1990, using interictal SPECT scan to assess children between 15 months and 9 years of age in their evaluation for hemispherectomy. Five patients had bilateral findings on surface EEG, one of whom also had bilateral abnormalities on MRI. To pursue hemispherectomy in these patients, we obtained an interictal SPECT scan and surface monitoring in all and depth monitoring in 3. All SPECT scans
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lateralized to the same hemisphere as the ictal discharges on invasive monitoring and did not show contralateral changes in the others, Hemispherectomy was performed on all 5 children and all are seizure free 6-20 months after surgery. This study demonstrates that SPECT scan is a significant adjunct in investigation for hemispherectomy. Lateralized findings on SPECT strongly support a favorable outcome regardless of surface E E G findings,
15. Scalp EEG abnormalities in relation to unilateral mesial temporal atrophy. - A. Gambardella, F. Cendes, J. Gotman and F. A n d e r m a n n (Montreal Neurological Institute, Montreal, Que., Canada)
Objectit,es. To assess the relationship between electroencephalographic abnormalities and mesial temporal atrophy in temporal lobe epilepsy (TLE). Background. MR1 volumetric studies show hippocampus and amygdala atrophy in many T L E patients. The role of this atrophy in the pathogenesis of T L E remains unclear and we attempted to relate it to E E G findings, Methods. We reviewed preoperative E E G s with scalp and sphenoidal electrodes in 27 T L E patients in whom MRI volumetric m e a s u r e m e n t s had shown unilateral amygdala a n d / o r hippocampus atrophy compared to matched controls. Results. Theta activity was observed in 2 3 / 2 7 patients but correluted poorly with atrophy (bilateral in 18/23). Delta activity was present in 2 3 / 2 7 patients and correlated well with atrophy (unilateral or clear ipsilateral predominance in 22/23). Spikes were found in 2 6 / 2 7 patients; they were ipsilateral to atrophy in 18 patients and bilateral in 8. 73 ictal onsets were analyzed: 34 (46%) were ipsilateral, 2 (3%) contralateral, 19 (26%) bilateral, and 18 (25%) undeterminate. Conclusion. T h e results show clearly that spikes and seizure onsets can be widespread or bilateral even in patients where unilateral mesial temporal atrophy is the only MRI abnormality. However, delta activity almost always coincides with the side of atrophy, Further investigations are required to establish the clinical significance of contralateral epileptiform activity.
16. Analysis of amygdaloid volume in patients with chronic temporal lobe seizures. - W.B. Bare a,b, p.j. Snyder b, M. Ashtari ¢ and N. Schaul a (Departments of a Neurology, b Psychiatry and c Radiology, Long Island Jewish Medical Center, New Hyde Park, NY) Results from recent research using M R imaging and computerized volumetric techniques have indicated that unilateral temporal lobe E E G foci are often accompanied by significant lateralized reductions in hippocampal volume. Very few studies have used computerized morphometry to examine the amygdala in patients with unilateral temporal lobe seizures. In this study, measures of left and right amygdaloid volumes were computed from flash M R images from 31 presurgical patients (16 left temporal, 15 right temporal) and 27 age- and sex-matched controls. A multivariate analysis of variance revealed a significant group by hemisphere interaction ( P < 0,001). Post hoc analyses indicated a lack of asymmetry in patients with right temporal lobe foci. Lateralized reductions in amygdaloid volume correctly predicted the laterality of the E E G seizure focus in 65% of the patient sample. Additional analyses revealed a high correlation between left and right amygdaloid volumes and a lack of correlation between amygdaloid and hippocampal volumes. O u r findings indicute that reductions of amygdaloid volume are associated with unilateral temporal lobe seizures, though the value of using these volumes to classify the laterality of the E E G seizure focus in surgical candidates remains unclear at this time.
17. Changes of the posterior tibial nerve somatosensory evoked potential in sleep. - M. Yeh, T. Yamada, Y. Noguehi, M. Matsubara, G. Shiraishi, S.-i. Kagimoto and N. U r u s h i b a r a (University of Iowa, College of Medicine, Iowa City, IA) We studied the changes of the posterior tibial nerve sensory evoked potential (PTN-SEP) topographically at various stages of sleep. Seven normal subjects had PTN-SEPs recorded from 16 closely spaced scalp electrodes (1.5-2 cm) centered at Cz, Standard peak nomenclature was used in assessing all SEPs which included P31, N35, N37, P40, N50, P31, P37 and P45. P31 and P35 were diffusely distributed but N37 was located at the contralateral hemisphere. P40 and N50 were paradoxically lateralized to the ipsilateral side. In all subjects, N37, P40 and N50 peaks showed a progressive latency prolongation (1.29 + 0.94 msec for N37, 1.68 ± 0.81 msec for P40, and 2.41 ± 1.04 msec for P50) with a concomitant increase in the N35-P40 peak-to-peak amplitude (1.08 ± 0.52 ~V) as stages 3 and 4 sleep were approached. R E M sleep showed a significant latency prolongation for N37 while P40 remained unchanged. Stages 1 and 2 of sleep showed no significant change in latencies or amplitudes when cornpared to the awake state. Previous studies on the median nerve have shown a similar pattern of latency prolongation. The latencies of the median N20 and P26 potentials behave in a similar m a n n e r to the tibial N37 and P40 respectively as noted above. These similarities in sleep may indicate these peaks to be analogous potentials between the two nerves. 18. Unique characteristics in the SEP recovery function for the pudendal nerve, - G. Shiraishi, T. Yamada, Y. Noguchi, M. Matsubara, S.-i. Kajimoto and N. Urshibara (University of Iowa College of Medicine, Iowa City, IA) Using a paired stimulus paradigm, we studied the recovery functions of somatosensory evoked potentials (SEPs) for the dorsal nerve of the penis (DNP-SEP) and found significant differences from other peripheral nerve SEPs. The paired stimuli, S1 and $2, were tested using interstimulus intervals (ISis) of l, 2, 5, 10, 30, 50 and 70 msec. The derived test ($2) response influenced by the preceding conditioning (1) stimulus was obtained by subtracting the response to a single stimulus (S1 only) from the response to a paired ( $ 1 + $ 2 ) stimulus. The recovery curves for the DNP-SEP were quite different from other SEPs. First, there was no significant suppression for stimuli of short ISis, except for 1 msec ISis where the DNP-SEP was noted to be almost absent. Second, the amplitude facilitation after 2 msec IS1 was far larger than that observed in other peripheral nerve SEPs. Finally, in contrast to the maximum suppression of other peripheral nerve SEPs at 30-50 msec ISI, the DNP-SEP showed maximum facilitation at 30 msec ISI. We propose that certain anatomical a n d / o r physiological characteristics are responsible for the remarkable amplitude facilitation of DNP-SEP. 19. Of mice a n d men: a case for brain-stem origin of short lasting nocturnal paroxysmal dystonia. - J.L. Burchfiel, G. Erha, C.D. Applegate, M.J. Berg a n d L. Oestreich (Comprehensive Epilepsy Program, University of Rochester, Rochester, NY) The pathogenesis and classification of "nocturnal paroxysmal dystonia" (NPD) remains obscure. It has been suggested that this syndrome represents a form of epilepsy, perhaps involving frontal or extrapyramidal structures. We present a case (patient MP) with a triad of symptoms: (1) a sleep disturbance characterized by frequent arousals from slow-wave sleep and, possibly, decreased R E M sleep; (2) arousals from slow-wave sleep accompanied by dyskinetic and dystonic movements (NPD); and (3) occasional tonic seizures occurring in association with the N P D episodes. The semiology of MP's tonic seizures is different from that typically seen in h u m a n general-
C E N T R A L A N D E A S T E R N A S S O C I A T I O N S OF E E G e r s SKI M E E T I N G ized seizure disorders and is essentially identical to that of mice receiving maximal electroshock (MES). MES tonic seizures in laboratory animals have been clearly demonstrated to depend on brain-stem structures. By analogy we suggest that MP's tonic seizures have a brain-stem origin. Most likely, MP's frequent arousals also involve brain-stem pathophysiology. Therefore, we advance the unifying hypothesis that all of MP's symptoms, including NPD, have a brain-stem origin involving structures which control s l e e p / w a k e f u l n e s s cycles and regulate associated muscle tone and movement. This case suggests that nocturnal paroxysmal dystonia is primarily a brain-stem sleep disorder,
20. Ietal SEEG propagation in surgically resistant temporal lobe epilepsy. - C. Adam, F. Richer and J.-M. Saint-Hilaire (Hfipital Notre-Dame, Montreal, Que., Canada) In temporal lobe epilepsy (TLE), studies using intracerebral seizure recordings (SEEG) have suggested that a short seizure propagation time to the contralateral temporal lobe is related to poor surgical outcome. However, our observations using a modified Talairach implantation method with electrodes in temporal and frontal lobes suggested that the first site of extratemporal propagation is most often the ipsilateral frontal lobe. We thus examined ictal SEEG characteristics in 3 matched groups of 7 T L E patients (resistants, cured, intermediate), taking into account the propagation to the frontal lobes. Resistant patients did not have any lesion outside the temporal lobe on CT scan or ictal S E E G characteristics of multifocality. Poor surgical outcome was related to: (1) the presence of widespread ictal onsets, (2) more frequent short ( < 1 sec) extratemporal propagation times, and (3) shorter m i n i m u m extratemporal propagation times (resistant group: 3.6 sec; cured group: 7.1 sec; intermediate group: 12.6 see). The data suggest that extent of SEEG ictal onset and speed of extratemporal (primarily frontal) propagation can be useful predictors of resistance to surgery for unilateral TLE. 21. Relationship between spike-waves and periodic leg movements in an adult with absence seizures. - B. Ehrenberg (Tufts University School of Medicine, Boston, MA) l have previously noted that adults with absence epilepsy have periodic leg movements (PLMs) of sleep. O n e such patient is a 30-year-old w o m a n whose nocturnal polysomnogram was examined in detail. The patient had a total sleep time (TST) of 7.4 h divided into 4 cycles 100-120 min in length with R E M at the end of each cycle but the second. There was an increased a m o u n t of stage 1 (21% of TST) at the expense of stage 2 (40%) and R E M (12%) while stages 3 - 4 were present in normal proportion (27%). There were 5
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brief awakenings. There were no apneas or hypopneas. There were 94 PLMs ( 1 2 . 7 / h of sleep); of these 60 (64%) were associated with arousals for a total arousal index of 8.7/h. There were 783 spike-wave bursts, usually seen as single or double complexes, at 2 3 Hz. The spike-wave complexes (SWCs) were densest in the first half of the night while the PLMs were clustered in the 3rd quarter of the night. Nevertheless, during the 3rd quarter, SWCs coincided with PLMs 59 times (63% of all PLMs), suggesting a shared trigger mechanism. Nine (15%) of the P L M / S W C pairings were also associated with an immediately following arousal pattern, not usually a feature of SWCs during sleep.
22. Electrocorticography for children with complex partial seizures undergoing excisional surgery. - P.A. Hwang, S.Y. Kwan, H. Otsubo and H.J. Hoffman (Bloorview Epilepsy Research Program and University of Toronto, Toronto, Ont., Canada) The role of intraoperative ECoG for excisional surgery in patients with intractable complex partial seizures has been recognised for over 50 years. Recently, however, a controversy arose over the value of post-excisional E C o G in adults undergoing anterior temporal lobectomy. We examined the question whether ECoG contributes to the surgical treatment of children with intractable complex partial seizures of temporal and extratemporal origin. In a retrospective study of 50 cases at the Hospital for Sick Children in Toronto undergoing excisional surgery between 1974 and 1991, all underwent E C o G at craniotomy, using a 4 x 4 or 4 × 5 electrode array under neuroleptic anesthesia (fentanyl and droperidol) from age 6 to 18 years, and general anesthesia under age 5 years with the nitrous oxide discontinued during the ECoG. For temporal lobectomy where the presurgical evaluation suggested mesial temporal dysfunction, depth electrode recording from the hippocampus at ECoG was also performed. There were 34 temporal and 16 extratemporal cases, with a follow up of 2 years or greater, and the seizure outcome was graded as I (seizure free, no drugs), II (seizure free, on drugs), III ( > 50% reduction), and IV ( < 50% reduction in seizures). Worthwhile iraprovement (grades I, II and II1 combined) was found in 3 0 / 3 4 cases (88%) after temporal lobectomy, and in 15/16 cases (93v/~) after extratemporal excision, but 1 died post-operatively. The post-excisional ECoG grade ( A - E ) did not correlate well with seizure outcome, although 2 cases with grade C (moderate residual epileptiform activity) had poor seizure outcome (grade IV) after temporal lobectomy, and 1 case after extratemporal excision. Although E C G is invaluable for localization of epileptogenic areas in both temporal and extratemporal excisions in children, its prognostic significance requires further study.